1. Field of the Invention
The present invention is related to a defrosting system for removing frost deposits from the cooling device (cooler) in a refrigerating system, specifically a defrosting system for removing the frost deposits using compressed air.
2. Description of the Related Art
Generally, cooling devices (cooler) are provided in a refrigerating system for cooling articles such as foodstuffs accommodated in a cold-storage room, and each of the cooler is composed of a cooling-coil onto the outer surface of which frost is deposited due to the moisture in the storage room. When frost is deposited on the cooling coil, the value of heat transfer coefficient decreases and as a result refrigerating capacity is reduced. Therefore, the frost deposited on the cooler must be removed at regular intervals.
A variety of methods are known for removing frost deposits from a cooling device. For example, there is known a method in which the flow of refrigerant is reversed so that the evaporator functions as a condenser. With this method, the cooling operation must be switched off during the defrosting operation and the articles such as foodstuffs accommodated in the storage room may be affected. There is also known a method in which an electrically heating coil is provided around the cooler (for example, a cooling coil) to melt and remove the frost deposited on the surface of the cooling coil. Further, there is known a method in which water is sprinkled onto the surface of the cooling coil to melt and remove the frost on the surface of the cooling coil.
In the above-mentioned methods, cooling operation must be stopped temporarily for removing the frost from the cooler. Therefore, an additional time is required for refrigerating the articles such as foodstuffs at least for the time period the cooling operation is stopped. That means that the time period required for refrigerating the articles such as foodstuffs increases.
On the other hand, an apparatus for recurrently removing frost deposits from cooling-coil batteries without stopping cooling operation for carrying out defrosting, is disclosed in U.S. Pat. No. 4,570,447(hereafter referred to as prior art 1), in which cooling coils are scanned by compressed pulsating air streams for removing frost deposits from the cooler. Further, in Japanese Laid-Open Patent Application No. 8-5207(hereafter referred to as prior art 2) is disclosed a defrosting apparatus in which rotating wings are provided to the rotating hollow shaft located in the air suction side of a cooling device, the rotating wings being rotated by the suction air flow sucked by the fan of the cooler, nozzles are provided to face the cooler, the nozzles being fixed to air blowing pipes attached to the rotating hollow shaft so that the air blowing pipes communicate to the hollow of the rotating hollow shaft, an air supply pipe is connected to the rotating hollow shaft by means of a rotary joint, and the discharge opening of an air compressor is connected to the air supply pipe. With this construction, the cooling coil is defrosted by compressed air.
In prior art 1, the defrosting is carried out by scanning the cooling coils with compressed pulsating air streams blowing out from nozzles. However, a plurality of nozzles are required in a refrigerating system in which a plurality of cooling coils are provided in a storage room. Therefore, if it is intended to supply compressed air to the nozzles by an air compressor, the capacity of the air compressor must be inevitably large, as a result, the cost of the defrosting system, in its turn the refrigerating system itself increases.
Further, with prior art 1, as compressed pulsating air streams are blown continuously to the cooler (cooling coils), the workload of the air compressor is high and energy efficiency is low. This is true also for prior art 2. Therefore, both prior art 1 and prior art 2 can not carry out the defrosting of cooler with low cost and high efficiency.